Solid-state imaging devices, which are widely used for video cameras and still cameras or the like, are provided in form of a package, in which an imaging element, such as a CCD or the like, is mounted on a base made of an insulating material, with the photo-detecting region being covered by a transparent plate. In order to make the device more compact, the imaging element is mounted on the base as a bare chip. FIG. 9 shows the solid-state imaging device disclosed in JP 2001-77277A, which is a conventional example of such a solid-state imaging device.
In FIG. 9, numeral 41 denotes a housing, which is made of a base 41a and frame-shaped ribs 41b formed in one piece by resin molding, thus forming an internal space 42. A die pad 43 positioned at the center of the base 41a and leads 44 positioned below the ribs 41b are embedded in the housing 41. An imaging element chip 45 disposed at the center of the internal space 42 is fixed to the upper side of the die pad 43. The leads 44 include inner terminal portions 44a that are exposed to the internal space 42 at the upper side of the base 41a on the inner side of the ribs 41b and outer terminal portions 44b that are accessible from the bottom side of the base 41a below the ribs 41b. The inner terminal portions 44a and the bonding pads of the imaging element chip 45 are connected by bonding wires 46 made of metal. A transparent sealing glass plate 47 is fixed to the upper surface of the ribs 41b, thus forming a package for protection of the imaging element chip 45.
This solid-state imaging device is mounted on a circuit board with the sealing glass plate 47 facing upward, as shown in FIG. 9, and the outer terminal portions 44b are used to connect it to the electrodes on the circuit board. Although not shown in the drawings, a lens barrel incorporating an imaging optical system whose relative position to the photo-detecting region formed in the imaging element chip 45 is adjusted with a predetermined precision, is mounted on top of the sealing glass plate 47. During the imaging operation, object light that has passed through the imaging optical system incorporated in the lens barrel is focused on the photo-detecting region and photoelectrically converted.
A solid-state imaging device with such a configuration is connected by the outer terminal portions 44b exposed at the bottom surface of the housing to electrodes on the circuit board, so that the height and the occupied surface area of the package are smaller than in configurations using a connection with outer leads bent downward from the sides of the housing, thus making it suitable for high-density packaging.
In the technology disclosed in JP 2001-77277A, an upper mold 48 and a lower mold 49 as shown in FIG. 10 are used to resin mold the housing 41 of the shape shown in FIG. 9. The upper side of the lower mold 49 is flat. The lower side of the upper mold 48 is provided with recessed portions 48a corresponding to the ribs 41b. An inner protruding portion 48b forming the internal space 42 and outer protruding portions 48c forming the outer surface of the ribs 41b are provided at both sides of the recessed portions 48a. The leads 44 and the die pad 43 are supplied in integrated form as a lead frame 50, and are disposed between the upper mold 48 and the lower mold 49.
By interposing the lead frame 50 between the upper mold 48 and the lower mold 49, a cavity 51 for molding the base 41a is formed between the lower mold 49 and the inner protruding portion 48b of the upper mold 48. In this state, a resin is filled in, and when the die opened and the molded product retrieved, the base 41a and the ribs 41b forming the housing 41 have their finished form. That is to say, as shown in FIG. 10, the recessed portions 48a of the upper mold 48 correspond exactly to the shape of the ribs 41b, and there is no additional finishing after molding. After the molding, the lead frame 50 is cut at locations positioned at the outer side of the ribs 41b. 
When fixing the seal glass plate 47 to the upper face of the ribs 41b in the above-described solid-state imaging device manufacturing process, an adhesive is applied on the upper face of the ribs 41b, as shown in FIG. 9, and then the seal glass plate 47 is positioned on the upper face of the ribs 41b and mounted. However, because the upper face of the ribs 41b is flat as shown in FIG. 9, and the ribs 41b are approximately 1 mm wide, the positioning of the seal glass plate 47 with respect to the flat upper face is difficult, and this is one cause of a drop in manufacturing efficiency.
In order to provide a wider margin of tolerance for positioning the seal glass plate 47, it is necessary that the upper surface of the ribs 41a has at least a certain width. Ensuring a sufficient width for the ribs 41b is an impediment to miniaturizing the area of the housing 41.